Filled crystalline resin blends typically have less than desirable impact properties. In addition it is difficult to prepare materials with a specific gravity greater than or equal to about 3.0 g./cc with good mechanical properties. In order to mimic articles made of heavy metals, such as zinc or steel, with a very heavily filled polyester resin it is also important that molded crystalline resin part have a smooth surface which can be easily plated using standard plating processes.
Holub et al, U.S. Pat. No. 4,122,061 describes polyester reinforced blends of poly(1,4-butylene terephthalate) and poly(ethylene terephthalate) impact modified with the addition of a polyolefin or olefin based copolymer resin. The polyolefinic resin is dispersed into the polyester blend and used for injection molding. Workpieces molded from such polyester resins are described as having a high degree of surface hardness and abrasion resistance, high gloss, and lower surface friction. It is desirable to provide further enhancements to the properties of resins of the type described in Holub et al.
U.S. Pat. No. 5,132,353 to Wallace describes a blend of thermoplastic polyester with from 50-75% zinc oxide. While the blends have useful mechanical properties and good surface appearance, specific gravity is below 3.0 g./cc. Similarly U.S. Pat. No. 5,149,734 to Fisher et al. describes polyester blends with 30-75% barium sulfate with ceramic like feel and density. In this case again specific gravity is below 3.0 g./cc, well below that of most metals. In both of the above patents no mention is made of metal plating.
U.S. Pat. No. 5,441,997 describes polyester molding compositions which have ceramic like qualities and high impact strength which can be easily molded. The composition is directed to a polybutylene terephthalate and/or polyethylene terephthalate and an aromatic polycarbonate with inorganic fillers selected from the group consisting of barium sulfate, strontium sulfate, zirconium oxide and zinc sulfate. If desired, a styrene rubber impact modifier can be added to the composition as well as a fibrous glass reinforcing filler. Although these compositions are suited for applications where ceramic like qualities are desired, it is desirable to achieve even higher densities while retaining desirable properties for molding.
Metal plating of plastics has been an area of study for many years and metal plated plastic articles are sold in a variety of applications: for instance, truck and automobile parts, appliances, electronic equipment, toys, handles, lighting reflectors and personal grooming equipment. As seen in U.S. Pat. Nos. 5,503,94 and 5,885,497 small changes in polymer structure, described as the presence of some aryl ester units in a polycarbonate copolymer, can have a major effect on plating. Plating and metalization of plastic articles still has a large element of unpredictability.
It is desirable to obtain an impact resistant polyester resin having a high specific gravity and enhanced plating properties. Additionally, it is desirable to achieve a smooth surface important to the final appearance of a metal plated article. Hence, it is desirable to provide improved resins containing additional ingredients which can enhance the above properties without detracting from desirable surface properties which can contribute to good appearance and plateability.